DE2061526A1 - Process for oxygen bleaching of lignocellulose materials - Google Patents

Description

The invention "relates to a method for the oxygen equation of lignocellulosic material aj such as J5" B "of wood pulps _s

Ignocellulosic materials in Paaerforra are widely used as raw material for the production of paper, cardboard, building boards, etc. "For many applications" the material is too dark in color and must be bleached. The darkness is caused by the presence of lignin which is present in the cellulose fibers of the material,

Bina bleaching is special in the case of iignoeellulosemateri · " alien required »those by the sulphate or Kraft process ■ have been produced * Sulphate pulp contains a considerable amount

109828/1574

BATH ORIGINAL

¹ anen lignin "This lignin speaks less auJf a chemiache treatment than the residual lignin in sulfite · Baa bleaching is actually a delignification * verfahron ₀ Usually used chlorine to the bleaching of L.ißnocellulosepulpen initiate an extraction after which represents chlorine treated Pulp with an alkali, such as sodium hydroxide, is followed by one or more oxidative or extrative processes. in order to produce a completely bleached pulp "The sequence: chlorination, alkali extraction, chlorine dioxide treatment, alkali" * extraction, chlorine dioxide treatment (it is abbreviated as c ^ EDED) is a typical technical process. Other sequences are also known, in which hypochlorite and alkali peroxide stages occur · Recently, bleaching sequences have been known which contain an alkaline oxygen stage · In the acid pulp treatment stage, the wood pulp is treated in an alkaline medium with oxygen gas under pressure. The oxygen stage can be preceded or followed by a chlorination stage .

In a normal kraft or sulphate pulp mill, in which the CEDBD bleaching sequence is used, the effluent from the bleaching plant results in £ 20 of the total biological oxygen demand produced by the mill. Furthermore, it is also a certain toxicity in the form of Chloropbenolen that are solubilized in the Chlorierungestufe generated "The main part of the Pulpendelignifizierung contributing» βtoffbedarf for biological Sauer, takes place in the alkali extraction stage _o The introduction of oxygen into the caustic extraction stage has an oxidative breakdown the organic residues result. Similar reactions take place in an alkaline oxygen stage before which no chlorination stage is undertaken. The outflows generated by the partial sequence CO and the outflows generated by the alkaline oxygen treatment (first stage) have a narrow one

10 98 26 / TS7 A BAD original

to each other, - the measurements of the biological oxygen s these discharges aeigen higher values than they can be obtained sub extrektionsstulea a conventional sequence _f like ε · Β »CEB«

Legislation in North America puts increasing pressure on the biological oxygen demand of all effluents to be reduced _. that'll gegleitet into public sewers n _t and can therefore "during alkaline Sauerstoffbehandlungbsobaohtete increasing prove unacceptable. Bine solution to the problem is to burn the effluents in Ablaugenrüekgewinnungssystem the pulp mill" However, if prior to the alkaline oxygen stage a chlorination "running stage is then burning Sine leads of the effluents sus this part bleach sequence a large amount of chloride in the burner of the Ablaugenrückgewinnungssystemse this results 3I explosion hazards. another difficulty with such a% stem linked eats _f is the possibility of retention of chlorides in the melt, which is generated by the waste liquor recovery system, with the result that chloride is built up in the system while the material is being circulated «

Conversely, when the alkaline oxygen treatment is the first stage of the bleaching sequence, then burning the effluents makes less Schwiering ^ gfcöiten, because that is ^one UaUn the chemical composition = · setting that of the liquor self-similar "is This has the ssusätzlichen advantage that liatriuiwerfcetoffe from the Melt are recovered and that they can be reused in the oxygen bleaching stage under certain circumstances. The incineration of the effluent from an alkaline oxygen lead stage carried out at the beginning thus brings economic and technical advantages with it. However, a single oxygen bleaching stage is not sufficient to bleach many wood pulps to the desired brightness and additional bleaching stages are required

BATH 109826/1574

'rtjinnen ". In these reagents are usually used;, the • ijh'l.or included, which in turn means problems with the elimination good of the stripping "

An oxygen / chlorination impregnation bleaching sequence has now been found in which a reduced amount of. chlorine-containing reagent is used and which can be integrated with a waste liquor nrUckgev / guild, "system of an associated PuXpenmühle" In this sequence, an alkaline Saueratoffbehandlung in t he first and used in the third stage _f wherein a special chlorine / Chlordioxid'-Beharidlung in the second stage and a chlorine dioxide ~ treatment in the fourth and final stage is used * * is the abbreviation therefor OC / D ~ O 'D _e the Abstrora from the oxygen treatment (first stage) is suitable for introduction into a AblaugenrückgewinnungssyBtem a pulp mill <, If the method according to the invention is used for bleaching a sulfate pulp, then a bleached product with a high Ilelliglceit value and a low reversion can be obtained «

The invention is therefore the object of an efficient process for oxygen bleaching LignoEellulosematerialien create au ^ wherein the effluent from the main oxidation step in the Ablaugenrückgewinnungssysteni a pulp mill may be introduced _o

The process of the invention comprises the following steps 1 ο Treatment of the lignocellulosic material in an aqueous alkaline medium with oxygen gas or with an oxygen-containing one Gas under superatmospheric pressure;

2o treatment of the oxygen-treated material in wäseeriger suspension with chlorine or chlorine dioxide or a mixture Aun chlorine and chlorine dioxide _t wherein the concentration of available Cblora in the range of Ο, Π σ kappa number χ of the oxygen-treated material to 0.30 Kappa number of sauerstoffbehahdelten material lies;

109826/1574 «dormin *.

3 * Treatment -as ehlox ·· - or chlorine dioxide treated nafcerials in aqueous alkaline medium with oxygen gas or a Oxygen-spherical gas under excessive pressure? and

4, treatment of the oxygen-treated material of stage 3 in aqueous .Suspension with chlorine dioxide

If this process is used to bleach wood pulp produced by sulphate processing, then the alkaline effluent from Stage 1 can be sent to a liquor recovery system. be fed to the pulp mill.

The alkaline Absfccom from stage 3 kaoa χα can be drained in the usual way, or it can be treated with lime * to precipitate organic residues, which are then separated * before the effluent is drained »

The treatment of the lignooellulosic material with Sauars fcoff is carried out with the pulped material in aqueous suspension at a consistency of 3 to 30%. The pulp is made alkaline by treatment with 1-5 Grew »-5 µ alkali, based on the pulp. At this point in time can the pulp also contain a preservative agent such as magnesium carbonate, magnesium oxide or magnesium hydroxide. be suspended ^ The. Alkaline pulp is then added to oxygen or oxygen-containing gas in a pressure vessel under an oxygen partial pressure in the range from 2 y1 to 14 _? 0 kg / cm nin and for a period of 10 to 45 »exposed at a temperature in the range of 100 to 200 ° 0 'when formulated taking place in low consistency Säuerstofföehaudlung the pulp is preferably stirred continuously * There v / IRAE preferably _t - the aqueous to treat pulp first with alkaline material ,, then exposing the oxygen under pressure ", and then the reaction mixture to the EeaktionstöHiperatui ¹ to 'bringein Bs has been found that this sequence a better Delegnifikation üqt results Lißnocellulosepulpe when ER is the case, if the "pulp before the läinfMhrung dos Sour toff .3 heated v ^ .Lrd" WADh] ^ i £ ^a .ndißi.m the Sauerstoffbehn rilun ^ "-; v / ix-ri the

109826/1574 ORIGINAL BATHROOM

Pulp in the ub "M <; h: 3r < v.oiße washed with water. «I> nr nl & aliache Outflow from α «? nvatan S huf β can the Ablaugenrüokgav / innun / 'ssyst a '5ugohQ.ri.gf !!': Fulpenmühlö supplied v / - ^ r the »

The treatment with chlorine or with chlorine dioxide οάαν with a mixture of chlorine and carbon dioxide v / ird at 10 to 40 ⁰ C with an aqueous pulp whose consistency is 3 to 30 ^[ } Ό ? out performed. The concentration of the chlorine or of the chlorine dioxide or of the chlorine / chlorine dioxide mixture is such that the available chlorine is in the range from 0.11 to 0 _? 30 multiplied by the kappa number of the oxygen-treated lignocellulosic material is “The kappa number is a hatred for the removal requirement of the lignin in the pulp to be bleached. The kappa number is determined by the procedure of Tappi Standard T-236. The weight ratio of chlorine to chlorine dioxide in the chlorine / chlorine dioxide mixture can be between 100: 0 and 100%. The weight ratio of chlorine to chlorine dioxide is in the range from 95: 5 to 80:20. The treatment requires 10 up to 60 min * The bleached pulp is then washed with water

In the second alkaline oxygen treatment, the pulp with a consistency of 3 to 30 % is treated with 1 to% alkali

and then treatment with oxygen or an oxygen-containing gas under a pressure of 2 _; 1 to 14 _? Subjected to 0 kg / cm. It is preferred ™ using a Yiskositätsbewahrungsaiittel su, v? Ie, for example, magnesium carbonate, Magnesiuraoxid or magnesium hydroxide ₀ The treatment is 10 to 30 minutes at a temperature in the range of ioO performed to 200 ° C, preferably being stirred ο The pulp is then reacted with '.Vaissor washed »

The pulp is then at a 3 to 30 ^ igon consistency; treated with Oj 1 to r, 0 # chlorine dioxide at 60 to 90 ⁰ C for a period of 1 to 4 hours. The pulp is then washed with water.

109826 / 1S74

SAD ORIGINAL

BeS. a typical treatment of a Kraft- or Äulfatholzpxöpo The following reaction conditions are used:

Stage 1s alkaline oxygen treatment The Hclapulpe is a lCcnsistenz of 6.0 $ 3 (0 yS Ratriuiahydroxid and 1j.ö $ föagnesiuracarbonat mixed "The alkaline pulp is enteric in a reactor at 15O ° C with air at a pressure of 14.0 kg / The pulp is then washed with water. The alkaline liquid and the abatrome from the washing are fed to the leaching system of the Pulpemnuhls.

The oxygen-treated pulp is 3.0 i * with a mixture of 2.16 # chlorine and 0.15 i ° chlorine dioxide over a period of 10 min then at a consistency sound _t at room temperature, the pulp is then washed with water "

Level 3ί Alkal isc he Oxygen fbeha MINATION

The Holspulp is at a consistency of 3 _? 0 ° with i 1 _f 75 mixed i> Hatiiumhydroacid · The alkaline pulp is then at 130 ° C in a reactor with air at 14 * 0 kg treated / cm for a period of 10 min under Rühren'der i / * The pulp ULPE is then washed with water.

Stage 4, 8 Ch lordioyid ^ Befaandliing

The wood pulp is treated with a consistency of 12 % with 0.4 # chlorine dioxide at 80 ° C. for a period of 3 hours

The alkali used in the first and second stages of the process is usually sodium hydroxide, but it is potassium faydroxide, sodium carbonate »potassium carbonate or calcium hydroxide suitable, The magnesium carbonate, magnesium oxide or magnesium hyaroxide, which is optionally used in the first stage of the process, inhibits the degradation of the lignocellulose pulp during oxygen treatment.

109826/1674 ^ AD original

- fc .- 2061528

Pas invent un ^ sge / iriPe "procedure yields ei. ^1. ? G ') Me ^s ohter; Ρι-ογ'-κϊ with ei nor tfufriaäden -'- ^ llenäei? Brightness ιuir! Viscosity, v / ohei gleinhzeii ί Λβ a / \ lnr roja geb-'IOu? t. will- the loiobt behendoH will be IvGrMi ₅ nw jrrnrx ^ inison outside , TfiitcrLin sj n.ü the cost of chmdkalien in diracu procedures- lower η U- in other soucr ^ toiTbleiohverfahren. bc? i deoen- eir; Pr with comparable lic) iigi - *; eit enaiolt v / ird,

! this Jjeschrtibun / j:.:; refer to the r / locations WUR üharainorisierimg the Hel31 ';;' jt, Kappa number and dor Tn ^ kositsi nvr wood pulp on the Vorto- get by the following methods.! became?

* Brightness; Tappi standard T 2 "\ 1 m,

2; H in,

Xap}; a -: '? -? Hl: Tappi-Staiidard T 2 ", ü

Viscosity Tappi ~ 8tanäard T ·? .3O sp?

Pi c-! .Ιοί! "J.ßkt: i.trarevftrsion j st the decrease ·! Of the brightness value,.

jenietsen is after the sample 1 st in a Z \ nati £ s> .x ™ ±; i ± - \; - 1 st fiX? .f. 105 ° G has been heated «

Ii 'dJefjer Bcöonrcä bunf, proportions relate to weight .; referring to the dry weight of the lignocellulo-ematerials, unless otherwise stated iöt _B

The iJrfindun ^ is elucidated in more detail by the following examples;

Be ^ iSjü ^ ejL ^ I

The Bleichabfü.lc " ^f ier invention (O - Ü / Ü-OL) was made with two anoloßen Sauer, '.: üoi'fbleichabfahrten toi -baren, närnlicl; with 0 C / DED and C / l'-t ¹ - ]) · -KI) ₁ Two samples ^ i.nor KrafthoÜ Kpnlpe v.'urdaii used: The sample I consisted of an Eastern Oanadiar Kraft pulp with a kappa number of 27 and an unbeaten viscosity of 35 »0 * The irobe II consisted of ai-ιε a Swedish Kraft pulp with a Ksppr; number of 35 _f 5 and oiaur u. ",: ^F -ble" .lc

1098? 6 / 1S74 8AD or _{1G (NAl}

Viscosity of 75 * 0 * The reaction conditions for the sequence 0-C / D-O-D were as follows: -

Pulp «I.

Temperature Consistency Sodium Hydroxide Magnesium Carbonate Lujrbdruek Time

It

e used a stirred hair actuator.,

ö / D l'instruction consistency chlorine

Time

O temperature

Sodium hydroxide Air pressure

A stirred reactor was used

temperature

12 «5 0.4 />

Z ^ ic 3 st

'Di ö iif.-al't .u:! £' Kt) fi (lin.yun ₍ ; -; iHi fir /: dio AMoljjö

Cblorclior ^ .d.

PuIgQ _- IJ ₁

130 O G 130 ° C. 6, O ■ 7.0 i> 3, 0 3.0 ° ß> 1" 0 1.0 i> 14, 0 atii 14.0 atü 10 min 10 min

space Rauia 3.0 Ji 3.0 # $ 2.16, 2.7 56. 0.15 / ° 0.18> & 10 miss 10 bin 130 ° C 130 ° C 3.0 9 & 3.0 # 1.75 $ 1.75; 14.0 atm 14.0 atm 10 min 10 min used 80 ° C ß0 ° G

12 fo

0.4 ^f / ₀ '3 st

, -!) wnren vis

109826-574

BATH ORIGINAL

■ r.

■ ff

temperature
consistency
Fa triumhydroxia
Magne s iumcar ^ or: .-. T
Air pressure
Time

A stirred reactor was used

C /: o temperature 50 ° G

Contra-tone; . 5, .0 ■% chlorine 2/16 f.

Oil dioxide 0.140; λ

Time 3 ft

2061526 PuIga ϊ PuXjoe ^ jEI 100-130 ° G 130 ° 0 6 1, '7 ff
I ρ "- < ..ν
J} Ο 3 a 1 f, Η.? 0 atii 14.0 atm 5 min Yorr-: vhit
15 min reaction 5 min pre-hit
ZVLUQ
15 min reaction

E 'temper ^ ture 60 ° C

Konsiötena 12.0 #! ⁱ Tacriumh.yrlr ^/ 'j: ii.] J, 5 ^

Time 1 1/2 h

D temperature 30 ° ο

Consistency 12 * 0 / o chlorine dioxide I * 0; '

Z-3it; · at

The he; .iktion £ 3bedirißunf; ön cür the \ bfo "lr: 5 ΰ / j; Ü""O ~ I5 ~ D vurua yi

50 ° C 5 , o io 2 0 .175% 3 at 60 ° C 12th , 056 1 ? 5 ^ 1 1/2 st 80 ⁰ G 12th _? 0> p 0 * 57i? "> ' j St.

0 / Ώ Temprji-ata-c i. »O ° c 20 ° 0

Κοπ.; ΠίυΐοηΗ ■ ^r . '0 i _y .' · =; ^ Q ^,

Ohio. V ^ ¹ > · ■ ^c; -0: 5

f> »μ.'u 10.: iu

109826/1574

BATH ORIGINAL.

AA

O 5! "Νϊ iiipe Χ · - ': ΐ Uj /

! ■ itf tar ack Celt

D temperature consistency Chlorine dioxide time

E temperature ICo ns is least sodium hydroxide Time

B temperature consistency chlorine dioxide Time

The results are given in Table I below

11 - 130 ° σ 2061526 ;> _? 0 % Pul "s II '■'' Π Cf.
S » -J />' 150 ° (J 14? 0 atu 7.0 $> 10 ■■ iniii 3 _? 0? T 80 ° C H »0 atü 12.0 ic 10 min $ 0.4, 80 ° C 3 st 12 _f $ 0 60 ° C 0.35 ^ 12.0; S. 3 st 0.3 i 60 ° Ci 1 1/2 st 12.0 io 80 ° 0 0 * 3 # 12.0 io 1 1/2 st 0.2? Έ 8O ⁰ C 3 st 12.0 io 0.2 ic 3 st

109826/1574

BATH ORIGINAL

Table I.

jsequence

Viscosity according to

the first stage

! Final brightness

j final revision

Bnd viscosity

Cost of oxygen demand, unbleached *

! Costs minus sour "! Substance level *

Pulp

! O-C / D-B-D C / "D-O" D ~ E ~ D

24.1

go _f o

17 * 6

23 * 5 90.2

2.7

9 »12

24.5 90.0

1.5 22.G

P.7.40

$ 4 _f 94

Costs for the tertiary chemicals

Chlorine 3.25

Sodium Hydroxide 3? 25

Chlorine dioxide 20.00 ^ / 1 » Calcium oxide 0 * 5 O-C / D-O-])

34.2
91.7

¹ Z (C

5.41

33.9 91.6

2.4

21 .6

ns.

91 * 5

34.0

on

Example II

Sine Bastern Ganadion Kraft pulp with a kappa number of 26 * 2 was bleached by swai process, namely 0-C / D-O-D and C / D-E-D-B-D · The reaction conditions for the following sequence O-C / D-O-D were as follows:

Temperature 119 C

Consistency $ 3

Sodium hydroxide 3 #

air pressure H, 0 atm

Time 10 min

A stirred reactor was used

G / D temperature 26 C

Consistency 3.25 #

Chlorine 3> 6 ^

Chlorine Dioxide $ 0.1

Time 10 min

l 'temperature 130 C consistency 3 ° J>

Sodium hydroxide 1 »75 ^

Air pressure 14.0 atm

Time. 10 min

D temperature 80 ° C

Consistency 12 #

Chlorine dioxide 0.5 9 δ

Time 3 h

109826/1574 bad original

The reaction conditions for the sequence C / DK - I) -E-!) Were as follows:

C / D temperature 20 C

Kona i punch 3 «: 3? S

Chlorine 4.75 1 °

Chlorine dioxide time

S temperature consistency sodium hydroxide time

D temperature Consistency chlorine dioxide time

B Temperature Consistency Sodium Hydroxide Time

D temperature consistency chlorine dioxide Time

Measurements of viscosity, brightness and brightness reversal were carried out on the pulp at the end of each of the bleaching sequences. In addition, in the case of the former Sequence the kappa number after the first level and the brightness

.109826 / 1S74

0 1 4, ⁰ ο 45 sin 60 , 5 f 12th 1/2 s-J: 3 ⁰ 0 1 £ ' 75 6 pounds 12th at 0, ⁰ σ 3 ever 60 5 1 » 12th 1/2 st 0, ⁰ C 1 i> 75 3 36 12th at 0, 3

naeL öfc-r cUiti ^

ßufe gGOies ^ en ... Hellißkeli; o; aeB «Uf * gen nach ä * .--. ·: 'cienaaoh Beh ^ ndl measure the pulp l ¹ Λ, Scheel

31 e results s: \ iio. in ia'bellr; XI approved ₀

table II

sequence 19. , -3 89.7 Xappa «v; a.hl after the
first study 60 _? 5 2 * 6 Brightness aach the
critteij level 89-4 24.0 E brightness 1f9 4 _? 0 ^ Emire version 16.4 4.75 # Final viscosity 4 _? ? 5? T 1.0 ^ öesarates consumed
KaOH 3 * 6 % GrBsaintes consumed CI2 0 _f 6 ^
.MVI ** ixmiLln IWIiIi'm >>. ¹ WOnI nu ^ lWI i * i '''»ι ■■ *»! Total GlOp consumed

It can be seen that the method according to the invention gives the same brightness? as the customarily used Bleichverfahx * _f ESS but less chlorine and chlorine dioxide less consumed

109826 / 157A

BATH ORIGINAL

Claims (2)

Claims 1a method for ϊί.ί ßiohurtg of Lignoeellulü ^ emateTl ^ iienj, ge · - ke naze I oh net. eux-ch the following stages? 1, treatment of the lignocellulosic material; *; in a watery one alkaline, j medium with oxygen gas or an oxygen-containing Gas under superatmospheric !!:. Pressure? 2, ·. Treatment of the oxygen-treated material in aqueous suspension with chlorine or chlorine dioxide or a mixture of chlorine and chlorine dioxide, the concentration of the * available chlorine in the range of ö _? 11 χ Kappa-Eabl of the oxygen-treated material up to 0.30 χ Kappa-number of the sa uer st of Γ'be ha nd e 1 te η Mate ri al · ** · ¹ <L sets? 3-, Treatment of the material treated with chlorine or with chlorine dioxide in aqueous / Meaxum with oxygen gas or an oxygen-containing one !! Gas under more than spherical pressure; and 4ο Treatment of the oxygen-treated material from stage 5 in aqueous suspension with chlorine dioxide _t 2c method according to claim K, characterized in »that the Lignosellulose material in stage 1 with 1-5 Ge \ v .- <$ alkaline "Material and, in aqueous suspension at a consistency Clay 3-3Ö wt .- ^, with oxygen or an oxygen-containing one 2 gas at an oxygen partial pressure of 2 _? 1 - 14 »0 kg / cm and at a temperature in the range of 100 ⁰ -200 ° C for a period of 10 to 45 minutes * Process according to claim 1, characterized in that the oxygen-treated material is treated in step 2 in aqueous suspension at a consistency of 3 to 30 Gewe-7 · ³ and at 10 to 40 ° G with a mixture of chlorine and chlorine dioxide, the The weight ratio of chlorine to chlorine dioxide is in the range from 100 to 0 to 0 * 100 109826/1574 BATH ORIGINAL mid wherein öiie treatment takes 10 to SO nVIN., Traversing a π aach claim 1, characterized in that da-i aauersto.ff material treated in step 2 in aqueous suspension "at a consistency of 3" to 20 'by weight * "; and 5' at 10 ti'fs .V) ⁰ C with a mixture of chlorine and chlorine dioxide, we treat <3 ₅ v / ob with the "weight ratio τοη chlorine au ghlordiox:! 2 in the range of 95: 5 to 80 % 20 and d wofeoi the treatment 'up to 60 min 'method according to -.Anspruch 1 ^ characterized in that dao chlorine oiled. Among other things, partly in stage 3 with 1 "to 5% alkaline material and, in v / ät / seriger suspensioa at consistena f / on 3 to 30% by weight, with oxygen or an oxygen-containing gas at an oxygen partial pressure is treated 00-200 ° C for a period τακ 10 bis- .30 min ^*; 2.1 Ms H kg / cm with stirring at a temperature in the range τ / ό ^"r? Method according to claim 1 _? characterized, -that during stage 4 the lignocellulose material in aqueous suspension at a consistency of 3 to 30 wt. ~ $ with O ₉ I to 1.0 Gev7 _e - $ chlorine dioxide at 60 to 90 ° C for a period of 1 to 4 st is treated. Method according to claim 1, characterized in that the lignocellulosic material is washed with water after each stage " Out 8 »^ ftacß claim 1, characterized gekennzeichnetj that the lignocellulosic material is made alkaline in the Steps 1 and 3 in that latriumhydroxid, Kaliumhydroxiäb _s sodium carbonate, potassium carbonate or calcium hydroxide is added. 109826/1574 The method of claim 1 wherein _s g-ökernuKaiaVinet. That during level 1 or 3 "» ■ arwsnde't will; wad sv; ar Magnesiuaicorebonat. oöex * .Ms'. 10a method according to claim 1, äaciureh gekennseichnetj that äpp, Lignocellulr.Bsiaaierial a wood pulpc; is, which has been horgeBlatted by U5.rs sulphate verfalroen. 109826/1574